using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using Umbraco.Core.Models;
using Umbraco.Core.Xml;
using umbraco;
using System.Linq;

namespace Umbraco.Web.PublishedCache.LegacyXmlCache
{
    internal class PublishedContentCache : IPublishedContentCache
	{
		#region XPath Strings

		class XPathStringsDefinition
		{
			public int Version { get; private set; }

			public static string Root { get { return "/root"; } }
			public string RootDocuments { get; private set; }
			public string DescendantDocumentById { get; private set; }
			public string DescendantDocumentByAlias { get; private set; }
			public string ChildDocumentByUrlName { get; private set; }
            public string ChildDocumentByUrlNameVar { get; private set; }
            public string RootDocumentWithLowestSortOrder { get; private set; }

			public XPathStringsDefinition(int version)
			{
				Version = version;

				switch (version)
				{
					// legacy XML schema
					case 0:
						RootDocuments = "/root/node";
						DescendantDocumentById = "//node [@id={0}]";
						DescendantDocumentByAlias = "//node[("
							+ "contains(concat(',',translate(data [@alias='umbracoUrlAlias'], ' ', ''),','),',{0},')"
							+ " or contains(concat(',',translate(data [@alias='umbracoUrlAlias'], ' ', ''),','),',/{0},')"
							+ ")]";
						ChildDocumentByUrlName = "/node [@urlName='{0}']";
						ChildDocumentByUrlNameVar = "/node [@urlName=${0}]";
						RootDocumentWithLowestSortOrder = "/root/node [not(@sortOrder > ../node/@sortOrder)][1]";
						break;

					// default XML schema as of 4.10
					case 1:
						RootDocuments = "/root/* [@isDoc]";
						DescendantDocumentById = "//* [@isDoc and @id={0}]";
						DescendantDocumentByAlias = "//* [@isDoc and ("
							+ "contains(concat(',',translate(umbracoUrlAlias, ' ', ''),','),',{0},')"
							+ " or contains(concat(',',translate(umbracoUrlAlias, ' ', ''),','),',/{0},')"
							+ ")]";
						ChildDocumentByUrlName = "/* [@isDoc and @urlName='{0}']";
						ChildDocumentByUrlNameVar = "/* [@isDoc and @urlName=${0}]";
						RootDocumentWithLowestSortOrder = "/root/* [@isDoc and not(@sortOrder > ../* [@isDoc]/@sortOrder)][1]";
						break;

					default:
						throw new Exception(string.Format("Unsupported Xml schema version '{0}').", version));
				}
			}
		}

		static XPathStringsDefinition _xPathStringsValue;
		static XPathStringsDefinition XPathStrings
		{
			get
			{
				// in theory XPathStrings should be a static variable that
				// we should initialize in a static ctor - but then test cases
				// that switch schemas fail - so cache and refresh when needed,
				// ie never when running the actual site

				var version = UmbracoSettings.UseLegacyXmlSchema ? 0 : 1;
				if (_xPathStringsValue == null || _xPathStringsValue.Version != version)
					_xPathStringsValue = new XPathStringsDefinition(version);
				return _xPathStringsValue;
			}
		}

		#endregion

		private static IPublishedContent ConvertToDocument(XmlNode xmlNode)
		{
		    return xmlNode == null ? null : new Models.XmlPublishedContent(xmlNode);
		}   

        private static IEnumerable<IPublishedContent> ConvertToDocuments(XmlNodeList xmlNodes)
        {
            return xmlNodes.Cast<XmlNode>().Select(xmlNode => new Models.XmlPublishedContent(xmlNode));
        }
		
    	public virtual IPublishedContent GetById(UmbracoContext umbracoContext, int nodeId)
    	{
    		if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");

    		return ConvertToDocument(GetXml(umbracoContext).GetElementById(nodeId.ToString()));
    	}

		public IEnumerable<IPublishedContent> GetAtRoot(UmbracoContext umbracoContext)
		{
			return (from XmlNode x in GetXml(umbracoContext).SelectNodes(XPathStrings.RootDocuments) select ConvertToDocument(x)).ToList();
		}

        public IPublishedContent GetSingleByXPath(UmbracoContext umbracoContext, string xpath, params XPathVariable[] vars)
        {
            if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");
            if (xpath == null) throw new ArgumentNullException("xpath");
            if (string.IsNullOrWhiteSpace(xpath)) return null;

            var xml = GetXml(umbracoContext);
            var node = vars == null
                ? xml.SelectSingleNode(xpath)
                : xml.SelectSingleNode(xpath, vars);
            return ConvertToDocument(node);
        }

        public IEnumerable<IPublishedContent> GetByXPath(UmbracoContext umbracoContext, string xpath, params XPathVariable[] vars)
        {
            if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");
            if (xpath == null) throw new ArgumentNullException("xpath");
            if (string.IsNullOrWhiteSpace(xpath)) return Enumerable.Empty<IPublishedContent>();

            var xml = GetXml(umbracoContext);
            var nodes = vars == null
                ? xml.SelectNodes(xpath)
                : xml.SelectNodes(xpath, vars);
            return ConvertToDocuments(nodes);
        }
        
        //FIXME keep here or remove?
		public IPublishedContent GetByRoute(UmbracoContext umbracoContext, string route, bool? hideTopLevelNode = null)
        {
			if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");
			if (route == null) throw new ArgumentNullException("route");

			//set the default to be what is in the settings
			hideTopLevelNode = hideTopLevelNode ?? GlobalSettings.HideTopLevelNodeFromPath;

			//the route always needs to be lower case because we only store the urlName attribute in lower case
        	route = route.ToLowerInvariant();

			var pos = route.IndexOf('/');
			var path = pos == 0 ? route : route.Substring(pos);
			var startNodeId = pos == 0 ? 0 : int.Parse(route.Substring(0, pos));
            IEnumerable<XPathVariable> vars;

            var xpath = CreateXpathQuery(startNodeId, path, hideTopLevelNode.Value, out vars);

			//check if we can find the node in our xml cache
		    var content = GetSingleByXPath(umbracoContext, xpath, vars == null ? null : vars.ToArray());

			// if hideTopLevelNodePath is true then for url /foo we looked for /*/foo
			// but maybe that was the url of a non-default top-level node, so we also
			// have to look for /foo (see note in NiceUrlProvider).
			if (content == null && hideTopLevelNode.Value && path.Length > 1 && path.IndexOf('/', 1) < 0)
			{
				xpath = CreateXpathQuery(startNodeId, path, false, out vars);
                content = GetSingleByXPath(umbracoContext, xpath, vars == null ? null : vars.ToArray());
			}

		    return content;
        }

        // FIXME MOVE THAT ONE OUT OF HERE?
		public IPublishedContent GetByUrlAlias(UmbracoContext umbracoContext, int rootNodeId, string alias)
        {
			if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");
			if (alias == null) throw new ArgumentNullException("alias");

			// the alias may be "foo/bar" or "/foo/bar"
            // there may be spaces as in "/foo/bar,  /foo/nil"
            // these should probably be taken care of earlier on

            alias = alias.TrimStart('/');
            var xpathBuilder = new StringBuilder();
            xpathBuilder.Append(XPathStringsDefinition.Root);

			if (rootNodeId > 0)
				xpathBuilder.AppendFormat(XPathStrings.DescendantDocumentById, rootNodeId);

            XPathVariable var = null;
            if (alias.Contains('\'') || alias.Contains('"'))
            {
                // use a var, escaping gets ugly pretty quickly
                var = new XPathVariable("alias", alias);
                alias = "$alias";
            }
			xpathBuilder.AppendFormat(XPathStrings.DescendantDocumentByAlias, alias);

			var xpath = xpathBuilder.ToString();

		    return GetSingleByXPath(umbracoContext, xpath, var);
        }

        public bool HasContent(UmbracoContext umbracoContext)
        {
	        var xml = GetXml(umbracoContext);
			if (xml == null)
				return false;
			var node = xml.SelectSingleNode(XPathStrings.RootDocuments);
			return node != null;
        }

        static XmlDocument GetXml(UmbracoContext umbracoContext)
		{
			if (umbracoContext == null) throw new ArgumentNullException("umbracoContext");

			return umbracoContext.GetXml();
		}

		static readonly char[] SlashChar = new[] { '/' };

        protected string CreateXpathQuery(int startNodeId, string path, bool hideTopLevelNodeFromPath, out IEnumerable<XPathVariable> vars)
        {
            string xpath;
            vars = null;

            if (path == string.Empty || path == "/")
            {
                // if url is empty
                if (startNodeId > 0)
                {
					// if in a domain then use the root node of the domain
					xpath = string.Format(XPathStringsDefinition.Root + XPathStrings.DescendantDocumentById, startNodeId);                    
                }
                else
                {
                    // if not in a domain - what is the default page?
                    // let's say it is the first one in the tree, if any -- order by sortOrder

					// but!
					// umbraco does not consistently guarantee that sortOrder starts with 0
					// so the one that we want is the one with the smallest sortOrder
					// read http://stackoverflow.com/questions/1128745/how-can-i-use-xpath-to-find-the-minimum-value-of-an-attribute-in-a-set-of-elemen
                    
					// so that one does not work, because min(@sortOrder) maybe 1
					// xpath = "/root/*[@isDoc and @sortOrder='0']";

					// and we can't use min() because that's XPath 2.0
					// that one works
					xpath = XPathStrings.RootDocumentWithLowestSortOrder;
                }
            }
            else
            {
                // if url is not empty, then use it to try lookup a matching page
                var urlParts = path.Split(SlashChar, StringSplitOptions.RemoveEmptyEntries);
                var xpathBuilder = new StringBuilder();
                int partsIndex = 0;
                List<XPathVariable> varsList = null;

                if (startNodeId == 0)
                {
					if (hideTopLevelNodeFromPath)
						xpathBuilder.Append(XPathStrings.RootDocuments); // first node is not in the url
					else
						xpathBuilder.Append(XPathStringsDefinition.Root);
                }
                else
                {
					xpathBuilder.AppendFormat(XPathStringsDefinition.Root + XPathStrings.DescendantDocumentById, startNodeId);
					// always "hide top level" when there's a domain
                }

                while (partsIndex < urlParts.Length)
                {
                    var part = urlParts[partsIndex++];
                    if (part.Contains('\'') || part.Contains('"'))
                    {
                        // use vars, escaping gets ugly pretty quickly
                        varsList = varsList ?? new List<XPathVariable>();
                        var varName = string.Format("var{0}", partsIndex);
                        varsList.Add(new XPathVariable(varName, part));
                        xpathBuilder.AppendFormat(XPathStrings.ChildDocumentByUrlNameVar, varName);
                    }
                    else
                    {
                        xpathBuilder.AppendFormat(XPathStrings.ChildDocumentByUrlName, part);
                        
                    }
                }

                xpath = xpathBuilder.ToString();
                if (varsList != null)
                    vars = varsList.ToArray();
            }

            return xpath;
        }
    }
}